Exodus 24:4-6

Living Bible

⁴ Moses wrote down the laws; and early the next morning he built an altar at the foot of the mountain, with twelve pillars around the altar because there were twelve tribes of Israel. ⁵ Then he sent some of the young men to sacrifice the burnt offerings and peace offerings to the Lord. ⁶ Moses took half of the blood of these animals and drew it off into basins. The other half he splashed against the altar.